Biological explanations of annorexia

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Outline and Evaluate the biological explanation of one eating
disorder (24 Marks)
Anorexia Nervosa (AN) seems to be associated with the role of serotonin
dysfunction. Abnormalities in serotonin levels are already known to be linked to
depression and anxiety. Bailer et al found higher serotonin activity in recovered
binge-purge anorexics. All the participants had slightly higher serotonin activity. But
the highest levels of serotonin in those showing the most anxiety. One suggestion is
that higher serotonin levels lead to more anxiety and actually starving oneself leads
to those serotonin levels lowering. AN then could be seen as almost a form of
serotonin. This may explain SSRIs that heighten the serotonin levels don't actually
work for many anorexics. However, they do work for some. Therefore, the exact
relationship between serotonin and anorexia is not understood. Malnutrition in any
case causes changes in levels and it is not cert ain whether serotonin imbalance
comes first or is actually the result of AN.
The role of genetics has also been examined by Holland et al (1984) who used a
sample of 40. They researched the genetic link by comparing MZ and DZ twins,
where one twin of each pair was suffering from AN. They hypothesized that as MZ
twins are genetically identical, if AN characterised entirely genetic, it should be a
shared trait. Holland et al. found a concordance rate of 55% for MZ twins and of only
7% for DZ twins. The significantly higher concordance rate for MZ twins suggests a
genetic involvement in AN, but clearly it is not the only component in place. If it was
entirely genetic, the concordance rate would surely have been 100%. Environmental
factors also are an implicating factor on whether an individual suffers from AN as MZ
twins are more likely to be treated similarly than DZ twins which in turn increases
the chances of both twins suffering from AN. However, Holland et al's research has
been supported by other research. Kendler et al. (1991) found similar results in their
twin study which in turn increases the reliability of Holland et al's study as a suitable
explanation for why people may develop AN.
There are also evolutionary explanations of AN that suggest some of the symptoms
and characteristics of AN are in our hard-wiring. The `Reproduction Suppression
Hypothesis' suggest that adolescent girls' desire to control their weight represents
an evolutionary adaptation in which ancestral girls delayed the onset of sexual
malnutrition in response to cues about the probability of poor reproductive success.
The ability to delay reproduction is adaptive because it enabled females to avoid
giving birth at a time when conditions aren't conductive to survival (e.g. famine).
In the `Adapted to Flee Hypothesis' Guisinger proposes that the typical AN symptoms
of food restriction and hyperactivity reflect the operation of adaptive mechanisms
that once caused migration in response to local famine. Normally when a person
begins to lose weight the body naturally conserves energy (becomes tired) and
hunger ensues. However, our ancestors who were nomadic foragers may have
needed to turn this mechanism off and be energetic despite the lack of food as this
would have increased their chance of survival. Having energy would have meant that
they could flee to another more favourable environment. In the EEA those starving

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Such ultimate approaches can be beneficial as it can help treatments be developed
and encourage parents to be more compassionate and less defensive. However, it is
problematic that AN could be passed on through natural selection when it ultimately
doesn't lead to survival but actually could lead to death. Also, the `Reproductive
Suppression Hypothesis' is gender biased in that it offers only an explanation of how
girls could develop AN when in fact boys develop it too.…read more

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